1. Field of the Invention
The present invention relates to a loaded weight measurement method and loaded weight measurement device for a dump truck.
2. Description of the Related Art
A method is known in the prior art (Japanese Patent Laid-open No. 61-34425) in which the weight of cargo is measured by detecting the load applied respectively to the front wheels and the rear wheels of a dump truck and correcting these detected loads on the basis of the angle of inclination of the vehicle and the center of gravity of the vehicle.
According to the prior art technology described in Japanese Patent Laid-open No. 61-34425, it is possible to determine the weight of a cargo simply by detecting the loads applied respectively to the front wheels and rear wheels. However, in this prior art technology, no consideration is given to the timing at which the loaded weight is measured, and hence the measurement timing is fixed.
A dump truck is used repeatedly to transport a cargo, such as sand, in a construction site or an excavation site, for example. The cargo loaded into the dump truck at the loading point is conveyed to a prescribed position by the dump truck, where it is then unloaded. When it has finished unloading, the dump truck returns to the loading point and is again loaded with cargo.
The dump truck repeats a work cycle of this kind. In order to ascertain the state of progress of the work or the operating efficiency of the dump truck, it is necessary to measure the weight of cargo transported by the dump truck (the transported weight) in each work cycle. In the present specification, the weight of the cargo transported by the dump truck is called the “transported weight”, in order to distinguish it from the loaded weight, which is a momentary measurement value.
In order to ascertain the state of progress of the work accurately, it is desirable that the transported weight is measured under uniform conditions every day. Therefore, it is possible to measure the transported weight in a relatively stable fashion if measurement is made during transportation when the dump truck is traveling, rather than in other circumstances. Consequently, in the prior art, the transported weight is measured only during travel of the dump truck (during transportation of the cargo).
However, there is no guarantee that the state is always stable during transportation, and depending on the work site, there may be cases where the truck has to travel along very rough roads having an extremely uneven road surface. When a truck is traveling along rough roads of this kind, the vehicle body sways significantly, and it is difficult to measure the transported weight accurately.
In particular, articulated type dump trucks which have swingably coupled front and rear vehicle bodies are often used in sites having rough terrain, such as mines, and hence they are subject to severe swaying during travel. Therefore, cases may arise where the transported weight cannot be measured accurately during travel.